Surgical devices are used in various open, endoscopic, and laparoscopic surgeries to manipulate tissue, staple tissue, and/or transect tissue volumes and blood vessels. These devices can include jaws for grasping tissue therebetween and, optionally, a cutting mechanism that can be advanced through the grasped tissue to transect it. The cutting mechanism can be designed to travel within a track formed in one or both jaws. In some instances the devices can also be used to seal tissue volumes and blood vessels being transected, for instance by applying electrical energy to the grasped tissue to seal it before tissue transection is completed. For example, various mono-polar and bi-polar radio frequency (RF) surgical instruments and surgical techniques have been developed for sealing tissue volumes and blood vessels. Electrodes can be disposed on a face of one or both of the jaws and can apply energy to the grasped tissue to promote hemostasis.
Many surgical devices configured to grasp tissue are configured such that squeezing a closure actuator causes jaws of a jaw assembly to close. Many different mechanical and/or electrical set-ups can allow for this set-up to be effective. For example, some surgical devices incorporate mechanical linkages between a closure actuator and jaws, and when a user manipulates the closure actuator by manually squeezing a trigger or lever arm, the jaws of the end effector can move from an open position to a closed position. In such configurations, however, high manual forces may be necessary for a user to operate the closure actuator, especially in a mechanically-actuated device. This can be problematic during a surgical procedure because a user may experience hand fatigue from repeatedly squeezing the closure actuator and/or having to hold the closure actuator adjacent to the stationary portion of the handle so that the jaws are in a closed position and compress tissue with the desired force. There is also a limit as to the amount of tissue compression that a user can achieve by manually squeezing a closure actuator. Still further, because devices having jaws inserted to a surgical site are generally held in a closed configuration to decrease the size of the profile of the device as it navigates through the body, a user often has to exert enough force on the closure actuator to hold the jaws in the closed position while navigating through the body.
Accordingly, there is a need for surgical devices and methods that can reduce the force required to actuate the device and/or reduce a user's hand fatigue during use.